package com.lgl.sqlSession.impl;

import com.lgl.config.BoundSql;
import com.lgl.prjo.Configuration;
import com.lgl.prjo.MappedStatement;
import com.lgl.sqlSession.IExecutor;
import com.lgl.utils.GenericTokenParser;
import com.lgl.utils.ParameterMapping;
import com.lgl.utils.ParameterMappingTokenHandler;

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class simpleExecutor implements IExecutor {

    private PreparedStatement getParamsPreparedStatement(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        // 1. 注册驱动，获取链接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4. 设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i + 1, o);
        }

        return preparedStatement;
    }

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchFieldException, IntrospectionException, ClassNotFoundException {

        PreparedStatement preparedStatement = this.getParamsPreparedStatement(configuration, mappedStatement, params);
        // 5. 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();
        // 6. 封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i < metaData.getColumnCount() ; i++) {
                //获取字段名
                String columnName = metaData.getColumnName(i);
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }

            objects.add(o);
        }

        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws ClassNotFoundException, SQLException, IllegalAccessException, NoSuchFieldException {

        PreparedStatement preparedStatement = this.getParamsPreparedStatement(configuration, mappedStatement, params);
        //执行sql
        int i = preparedStatement.executeUpdate();
        return i;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if (paramterType != null) {
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }

        return null;
    }

    /**
     * 完成#{}的解析工作 1，将#{}解析成?,  2.解析出#{}的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);

        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);

        //#{}解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);

        return boundSql;
    }
}
